package org.bouncycastle.asn1;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

/**
 * Base class for an application specific object
 */
public class DERApplicationSpecific extends ASN1Object {
    private int tag;
    private byte[] octets;

    public DERApplicationSpecific(int tag, byte[] octets) {
        this.tag = tag;
        this.octets = octets;
    }

    public DERApplicationSpecific(int tag, DEREncodable object) throws IOException {
        this(true, tag, object);
    }

    public DERApplicationSpecific(boolean explicit, int tag, DEREncodable object) throws IOException {
        ByteArrayOutputStream bOut = new ByteArrayOutputStream();
        DEROutputStream dos = new DEROutputStream(bOut);

        dos.writeObject(object);

        byte[] data = bOut.toByteArray();

        if (tag >= 0x1f) {
            throw new IOException("unsupported tag number");
        }

        if (explicit) {
            this.tag = tag | DERTags.CONSTRUCTED;
            this.octets = data;
        } else {
            this.tag = tag;
            int lenBytes = getLengthOfLength(data);
            byte[] tmp = new byte[data.length - lenBytes];
            System.arraycopy(data, lenBytes, tmp, 0, tmp.length);
            this.octets = tmp;
        }
    }

    private int getLengthOfLength(byte[] data) {
        int count = 2; // TODO: assumes only a 1 byte tag number

        while ((data[count - 1] & 0x80) != 0) {
            count++;
        }

        return count;
    }

    public boolean isConstructed() {
        return (tag & DERTags.CONSTRUCTED) != 0;
    }

    public byte[] getContents() {
        return octets;
    }

    public int getApplicationTag() {
        return tag;
    }

    public DERObject getObject() throws IOException {
        return new ASN1InputStream(getContents()).readObject();
    }

    /**
     * Return the enclosed object assuming implicit tagging.
     * 
     * @param derTagNo
     *            the type tag that should be applied to the object's contents.
     * @return the resulting object
     * @throws IOException
     *             if reconstruction fails.
     */
    public DERObject getObject(int derTagNo) throws IOException {
        if (tag >= 0x1f) {
            throw new IOException("unsupported tag number");
        }

        byte[] tmp = this.getEncoded();

        tmp[0] = (byte) derTagNo;

        return new ASN1InputStream(tmp).readObject();
    }

    /*
     * (non-Javadoc)
     * @see org.bouncycastle.asn1.DERObject#encode(org.bouncycastle.asn1.DEROutputStream)
     */
    void encode(DEROutputStream out) throws IOException {
        out.writeEncoded(DERTags.APPLICATION | tag, octets);
    }

    boolean asn1Equals(DERObject o) {
        if (!(o instanceof DERApplicationSpecific)) {
            return false;
        }

        DERApplicationSpecific other = (DERApplicationSpecific) o;

        if (tag != other.tag) {
            return false;
        }

        if (octets.length != other.octets.length) {
            return false;
        }

        for (int i = 0; i < octets.length; i++) {
            if (octets[i] != other.octets[i]) {
                return false;
            }
        }

        return true;
    }

    public int hashCode() {
        byte[] b = this.getContents();
        int value = 0;

        for (int i = 0; i != b.length; i++) {
            value ^= (b[i] & 0xff) << (i % 4);
        }

        return value ^ this.getApplicationTag();
    }
}
